The present invention relates to an apparatus for heating hot water.
The usual method for heating hot water for residential and commercial purposes is to use a vertically orientated cylindrical hot water tank with a convex metallic base plate. An atmospheric burner fed by an external gas or oil supply is usually positioned immediately beneath the base plate. On command, triggered by an internal thermostat, the atmospheric burner ignites. Heat from the flame of the atmospheric burner conducts through the base plate and warms the water inside the hot water tank. Hot air, products of combustion and un-burnt gases are channeled into a vertical flue which vents them into the external atmosphere. During operation flue temperatures on conventional hot water heaters can often be as high as 300xc2x0 C. Conventional hot water heaters are generally supplied with cold water by means of a vertically descending feed pipe that injects cold water into the hot water tank in an area proximate to the base plate. At the top of the hot water tank is an out-take valve which removes hot water from the tank when needed. When the atmospheric burner is ignited the water at the bottom of the tank is heated and it rises to the top of the tank. When the burner is turned off, there is a convective mixing of the hot and cold water and the water temperature equalizes throughout the tank.
The disadvantages of such conventional systems are considerable. The use of an external atmospheric burner in conjunction with a metallic base plate greatly reduces heat exchange efficiency. A considerable amount of stand-by heat loss is experienced and further heat is lost through the flue system into the external atmosphere. Also, the base plate has a relatively small surface area that is in contact with the water inside the tank. The use of an external burner and flame in an enclosed room also poses obvious safety risks. Further, because the flame impinges directly on the external surface of the hot water tank, the potential to use different types of materials to construct the hot water tank is greatly restricted and removes including the ability to use high efficiency insulating materials such as composite fiberglass. Finally, a large disadvantage of conventional hot water heaters is the inability to provide consistent supplies of hot water at varying temperature ranges. Many modern residential properties utilize hydronic heating systems which require differential hot water temperature supplies. Commercial operations also often require hot water of varying temperatures. With a conventional system the hottest water is simply drawn from the top of the tank and as previously discussed, convection and mixing often result in the hot water tank containing water at one uniform temperature throughout.
There have been attempts to create hot water heaters that overcome some of these problems. Hot water heaters have been developed that utilize an internal coil system to heat the water instead of using an external atmospheric burner. Hot gas or hot liquid is forced through a hollow coil which transmits the heat into the surrounding water. The use of an internal coil system greatly raises efficiency and alleviates many of the problems encountered using an external atmospheric burner. Stand by heat loss is virtually eliminated, a far greater heating surface area is exposed to the water and the dangers associated with using an external open flame are largely addressed. Further, because the external surface of the tank is not being heated, a broadened choice of construction materials is available. However, these hot water heaters all utilize a single internal coil system, and like the prior conventional hot water heaters, they are unable to provide constant and reliable supplies of hot water of varying temperatures. Further, as with the conventional hot water heater, there will be tendency for the hot water to mix resulting in a single uniform temperature within the tank.
U.S. Pat. No. 4,203,392 teaches the use of a single heating coil with a physically divided hot water tank such that there is an upper hot tank and a lower cold tank. However, this device is capable of only supplying hot water of one temperature. Further, the separated areas cannot be exclusively heated, and they can only be heated at the same time with the single heating coil.
There is a need in the art for an efficient hot water heating apparatus that utilizes the advantages of an internal coil heating system but that has the capability of providing reliable and steady supplies of hot water of varying temperatures.
The present invention is directed to an apparatus for heating water.
Accordingly, in one aspect of the invention, the invention comprises a water heating apparatus comprising:
(a)a water storage tank having a cold water inlet and having at least two hot water outlets;
(b)at least two hollow heating conduits, each conduit passing into the tank from an exterior position, traveling through the interior of the tank and exiting out of the tank, wherein a first conduit is associated with a first heating zone and a second conduit is associated with a second heating zone, the heating zones being vertically stacked;
(c)each conduit having an inshot gas burner associated with the hollow conduit; and
(d)means for independently turning each inshot gas burner on or off.
In a preferred embodiment the individual conduits may be helically coiled within the interior of the tank between their entry position and their exit position. The independent gas inshot burners may be regulated by at least two aquastats placed in the interior of the tank. As well, each distinct heating zone may have an associated hot water outlet. In one embodiment, the conduits may feed into a common exhaust flue containing a trap and drain to catch condensation in the exhaust gases. In one embodiment, the exhaust flue may contain a fan to draw the exhaust gases through the hollow conduits. In another embodiment, the helical coils of the individual conduits may overlap and fit together such that there may be more than one individual conduit associated with each heating zone.